Biology Chapter on Thermoregulation

Metabolism in Conformers and Regulators (Abiotic Factors)

• Abiotic factors significantly affect an organism's metabolic rate. Key abiotic factors include pH, temperature, salinity, and moisture.
• An organism's ability to maintain a constant metabolic rate is reliant on external environmental factors.

Conformers

• Conformers' internal environments directly reflect their external environment.
• Examples include snakes, lizards, and frogs.
• The metabolic rate of a conformer is highly dependent on environmental parameters like temperature and salinity.
• Conformers have low metabolic costs because they don't regulate internal conditions.
• A disadvantage is a limited ecological niche, as they are less adaptable to changes in the environment.
• Conformers use behavioral strategies like basking in the sun to maintain optimal metabolic rate.
• Some conformers use behavioural responses for regulating and maintaining an optimal metabolic rate.

Regulators

• Homeostasis, a key aspect of regulators, maintains internal environment stability (e.g. constant body temperature).
• Regulators use metabolic energy and mechanisms to control their internal environments, regardless of external variations.
• Examples include dogs, koalas, and certain fish.
• Regulatory mechanisms incur higher metabolic costs.
• An advantage is that regulators can occupy a broader range of ecological niches.

Negative Feedback Control

• Homeostasis is maintained by negative feedback mechanisms.
• Negative feedback maintains a stable internal environment, even with external changes. (e.g., temperature, 37°C)
• Regulators need energy for homeostasis.
• The hypothalamus plays a central role in temperature regulation

Thermoregulation

• Thermoregulation is a negative feedback mechanism.
• Mammals maintain a consistent body temperature of 37°C.
• The hypothalamus monitors and controls body temperature.
• When body temperature increases, corrective responses like vasodilation and increased sweating are initiated.
• When body temperature drops, responses like vasoconstriction, shivering, and increased metabolic rate occur.

Surviving Adverse Conditions (Predictive and Consequential Dormancy)

• Adverse conditions disrupt normal metabolic activity.
• Some organisms survive by reducing their metabolic rate (dormancy).
• Dormancy can be predictive (acting before conditions change) or consequential (following condition change).
  • Examples:
    • Hibernation (predictive) — survival in cold conditions with low food availability.
    • Aestivation (predictive) — survival in high temperatures and drought.
    • Daily torpor (consequential) — temporary reduction in metabolic activity for some mammals.
• Trees respond to environmental cues to reduce growth in autumn to prepare for winter (predictive).

Avoiding Adverse Conditions (Migration)

• Migration helps organisms avoid adverse metabolic conditions.
• Migration involves relocating to a more favorable environment.
• Migration involves energy expenditure, which is a high metabolic cost.
• Examples: birds, whales, turtles, caribou.
• Various techniques are employed to study migration (e.g., bird banding, satellite tracking).

Microorganisms (Growth and Metabolism)

• Microorganisms utilise a range of substrates for metabolic processes.
• They generate diverse products from their metabolic pathways. They are adaptable, readily cultivated, and rapid in growth.
• Microorganisms are utilized in industrial processes for generating a wide variety of products.
• Specific environmental factors like nutrient availability, pH, temperature, and oxygen concentration critically influence their growth and metabolic rates.

Growth Phases (Microorganisms)

• Microbial growth follows distinct phases (lag, log, stationary, death)
• The lag phase has slow growth, as enzymes are induced for processing new substrates.
• The log phase shows the fastest growth rate enabled by plentiful nutrients.
• The stationary phase occurs when nutrients dwindle, and toxic secondary metabolites accumulate.
• The death phase features decreasing cell numbers due to significant nutrient depletion and buildup of toxic wastes.

Secondary Metabolites

• Secondary metabolites are synthesized during the stationary phase of microbial growth. They are not essential for the organism's growth or reproduction.
• Some secondary metabolites possess ecological benefits, such as aiding in competition with other microbes or deterring other organisms.
• Some secondary metabolites are valuable to humans, e.g., antibiotics or industrial chemical compounds.

Prokaryotes vs Eukaryotes

• Prokaryotes (bacteria and archaea) possess circular DNA and plasmids, whereas eukaryotes (e.g., animals, plants, and yeasts) have linear DNA in a nucleus and circular chromosomes in organelles (mitochondria, chloroplasts).
• Yeast cells' DNA structure is similar to eukaryotes but also incorporates plasmids.

Strain Improvement

• Techniques such as mutagenesis and recombinant DNA technology alter wild strains of microorganisms to better meet industrial production needs.
• Mutagenesis is inducing mutations in microorganisms through exposure to mutagens.
• Recombinant DNA technology involves introducing foreign genes into the microorganisms.